The subject matter disclosed herein relates to magnetic resonance imaging equipment (MRI), and more specifically, to systems that provide accurate high power currents to, for example, drive gradient coils.
This section is intended to introduce the reader to certain aspects of art that may be related to aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it may be understood that these statements are to be read in this light, and not as admissions of prior art.
Magnetic resonance imaging (MRI) is an imaging modality that is often used to generate images (e.g., spatial maps) based on the distribution of molecules in a subject. Generally, an MRI image of a subject (e.g., a patient) is produced by measuring properties of the gyromagnetic materials of the subject, such as hydrogen nuclei. These properties are usually obtained by measuring emissions from the gyromagnetic materials within the subject in response to an excitation from applied magnetic fields. The magnetic fields used for excitation generally include a strong primary magnetic field, magnetic field gradients, and radiofrequency (RF) magnetic field excitation pulses. Of note, the magnetic field gradients may be used by the MRI system to provide spatial encoding to the acquired data. To that end, the gradient coils may be used to generate spatial gradients of magnetic fields such that spatial coordinates of the subject may be associated with a locally encoded magnetic field value. As a result of this magnetic field-based encoding, the emission from the gyromagnetic materials may contain information that may be used to inform the spatial origin of a particular emission during image reconstruction.
The magnetic field gradients may be obtained by driving specific currents to the gradient coils. More specifically, these magnetic field gradients may be controlled by adjustment of the currents in the gradient coils that are responsible for generating magnetic fields. Magnetic coils may be associated with each one of spatial axes, the x-axis, the y-axis, and the z-axis, and the current in each of the axis coils may be independently controlled during the course of the data acquisition, to obtain flexible three-dimensional slicing of the images. To generate the currents in the magnetic coils, magnetic coil drivers may be used. A magnetic driver may include a gradient power supply and a gradient amplifier (e.g., a current amplifier) that can induce currents in the magnetic coil. Magnetic coil drivers may demand very accurate currents for precise, high-resolution spatial encoding. Moreover, the currents and voltages required to drive the current in the magnetic coils can be very large and varying. As a result, the design for the power supplies in these systems may be particularly challenging due to the large current changes and the large voltages normally used by the amplifiers.